clang -std=c23 incorrectly treats int (*)(struct { int i; }) and int (*)(struct { int i; }) as compatible types when they are types of struct members being compared for compatibility

Declaring `x` twice in the same compilation unit :

```c
struct s { int (*f)(struct { int i; } ); } x;
struct s { int (*f)(struct { int i; } ); } x;
```

Clang accepts ([CE link](https://gcc.godbolt.org/z/jqor3xson)). GCC rejects because the struct with the member `i` being tagless, its first declaration is not compatible with its second declaration. The above should be rejected for the same reason `struct { int i; } y; struct { int i; } y;` should be rejected (Clang correctly rejects this latter example).

The most relevant clause in C23 is https://cigix.me/c23#6.2.7.p1

EDIT: as noted by anematode, `clang -std=c23` also [fails to reject the simpler code below](https://gcc.godbolt.org/z/hYTM1T1W6):

```c
struct s { struct { int i; } b; } x;
struct s { struct { int i; } b; } x;
```

Also, since I wrote the program for another discussion, the problem is not just that Clang accepts programs that it should reject. It produces the wrong code for valid C23 programs, too: https://gcc.godbolt.org/z/36c4r8Y53